1. Field of the Invention
The present invention relates to an internal combustion engine having an engine body and provided with an electrical equipment holder which holds electrical parts and is attached to the engine body. More specifically, the present invention relates to an internal combustion engine intended for use on, for example, an outboard motor, and to a construction of an electrical equipment holder attached to the internal combustion engine.
2. Description of the Related Art
An internal combustion engine is provided with many electrically operated engine parts (hereinafter, referred to as “electrical engine parts”) including spark plugs and a fuel supply system. As disclosed in, for example, JP-A 10-176541 and JP-A 2001-260983, an electrical equipment holder, which holds electrical parts including a control unit and couplers connected to the electrical engine parts, is attached to the engine body of an internal combustion engine.
The number of electrical engine parts of the internal combustion engine mounted on a machine has progressively increased with the development of electronic control systems for the electronic control of operations of the internal combustion engine. Consequently, the number of electrical parts connected to the electrical engine parts has increased or the sizes of the electrical parts have increased. Many engine parts of engine accessories including an intake system, a cooling system and a lubricating system are arranged around the engine body. If the electrical parts are held in a planar arrangement in an electrical equipment holder, the electrical equipment holder becomes inevitably large. When the internal combustion engine provided with the large electrical equipment holder is incorporated into a comparatively small machine, such as an outboard motor, it is difficult to secure a space for the large electrical equipment holder around the engine body.
When electrical parts held in the electrical equipment holder include an electric control device, heat generated by the electric control device affects the performance of the other electrical parts. The electrical equipment holder needs to be formed in a large size if the electric control device is merely separated from the other electrical parts in a plane to reduce the thermal influence of the electric control devices on the electrical parts and to ensure efficient dissipation of heat generated by the electric control devices.
Increase in the size of the electrical equipment holder resulting from the planar arrangement of electrical parts in the electrical equipment holder may be prevented by contiguously placing other electrical parts on the electrical parts attached to the electrical equipment holder. However, such a layered arrangement of the electrical parts entails the following problems attributable to the contiguous, layered arrangement of the other electrical parts. The other electrical parts are susceptible to vibrations generated by the operation of the internal combustion engine because it is difficult to fixate the other electrical parts securely and it is possible that the electrical parts rub each other. When the electric control device is attached to the electrical equipment holder, the electrical part contiguous with the electric control device is liable to be subject to the thermal influence of the electric control device. Thus measures for avoiding the thermal influence of the electric control device on the electrical part are necessary and the dissipation of heat generated by the electric control device is reduced.
It is desirable to reduce the influence of the deformation of the electrical equipment holder and vibrations generated by the operation of the internal combustion engine on the electric control device in order to insure the reliability of the electric control device.
There are engine parts smaller than the electrical equipment holder, which is one of the engine parts and include a thermostat valve of the cooling system of the internal combustion engine. Such engine parts will be referred to as small engine parts. The small engine parts are disposed on the outer side of the engine body and are detachably attached to the engine body. The small engine parts can be easily removed from the engine body for maintenance when the electrical equipment holder is disposed not to obstruct the removal of the small engine parts. However, many other engine parts are disposed on the outside surface of the engine body and hence it is difficult to secure a proper space for the electrical equipment holder.
The present invention has been made under such circumstances and it is therefore an object of the present invention to facilitate securing a space, in which an electrical equipment holder can be installed, outside the engine body of an internal combustion engine.
Another object of the present invention is to facilitate securing a space for an electrical equipment holder by attaching a plurality of electrical parts in layers to the electrical equipment holder to form the electrical equipment holder in a small size and to solve problems resulting from the contiguous arrangement of the electrical parts.
A further object of the present invention is to provide an electrical equipment holder capable of being installed in a small space around the engine body of an internal combustion engine, of holding an electric control device and electrical parts such that the thermal influence of the electric control device on the other electrical parts is reduced and heat generated by the electric control device can be effectively dissipated, of being formed in a small size so that a space for the electrical equipment holder can be easily secured, and of facilitating securing a space for the electrical equipment holder by being disposed so as to cover engine parts in a direction in which the engine parts are removed from the engine body.